What survives here is so worn by time that the enclosure barely announces itself above the surrounding pasture, yet the geometry is still readable if you know what you are looking at: a roughly circular raised interior, roughly twenty metres across, that was once defended by a bank, a fosse, and an outer bank beyond that.

The monument is a rath, the most common type of early medieval settlement in Ireland. A rath typically consisted of a circular area enclosed by one or more earthen banks and ditches, the fosse being the ditch dug to provide material for the bank, and the whole arrangement serving as a farmstead boundary as much as a defensive structure. At Colgagh, the internal bank of earth and stone survives best along the north-east to south-west arc, while the north-north-west to north-east stretch has disappeared almost entirely, its line now marked only by a relic drystone wall running roughly west-north-west to east-south-east. The fosse, at around 1.35 metres wide, is most legible on the south-east to south-west side; elsewhere it has been reduced to the faintest of impressions. The outer bank, modest to begin with at around a metre wide, has likewise faded on most sides. The original entrance cannot now be identified. At the centre of the slightly domed interior sits the remains of a hut site, the footprint of the dwelling that once stood within this enclosure, making the domestic scale of the place quietly legible even in its diminished state.

The site sits on a gentle south-facing slope in low-lying undulating pasture, a landscape that would have offered reasonable grazing and proximity to the lough. The slight natural rise on which the rath stands would have given its occupants a modest vantage point over the surrounding ground, which is precisely the kind of unspectacular but practical positioning that characterises so many of these early medieval farmsteads across the Irish countryside.